Compressed-air electric apparatus embodying a drying device

ABSTRACT

Compressed-air electric apparatus such as a circuit interrupter having a compressor to compress air taken from a low-pressure vessel. The pressure in said vessel is close to the atmospheric pressure and an inlet valve controls the admission of atmospheric air to said vessel as the pressure therein drops below a predetermined value upon functioning of the compressor in case of leakage of high-pressure air. A drying device dries the air supplied by the compressor. The result is a substantially closedcircuit air circulation relieving the drying device without needing an absolutely hermetic sealing.

United States Patent Inventor (M11195 Grenoble, France Appl. No. 867,012 Filed Oct. 16, 1969 Patented Nov. 9, 197 l v Assignee Merlin Gerin, Soeiete' Anonyme Grenoble, France Priority Nov. 6, 1968 France 172,839

COMPRESSED-AIR ELECTRIC APPARATUS EMBODYING A DRYING DEVICE 4 Claims, 1 Drawing Fig.

References Cited UNITED STATES PATENTS 2,757,261 7/1956 Lingal et al. 200/ 148 B 2,890,312 6/1959 Forwald 200/148 B 3,359,390 12/1967 Frowein 200/148 E Primary Examiner-Robert S. Macon Attorney-Stevens, Davis, Miller & Mosher ABSTRACT: Compressed-air electric apparatus such as a circuit interrupter having a compressor to compress air taken from a low-pressure vessel. The pressure in said vessel is close to the atmospheric pressure and an inlet valve controls the admission of atmospheric air to said vessel as the pressure therein drops below a predetermined value upon functioning of the compressor in case of leakage of high-pressure air. A drying device dries the air supplied by the compressor. The result is a substantially closed-circuit air circulation relieving the drying device without needing an absolutely hermetic sealmg.

l l l l l l l ll l COMPRESSED-AIR ELECTRIC APPARATUS EMBODYING A DRYING DEVICE The present invention relates to compressed-air electric apparatus disposed in atmospheric air and comprising a highpressure compressed air enclosure and a contiguous low-pressure air vessel and compressor means compressing air taken from said low-pressure vessel to supply compressed gas to said high-pressure enclosure.

ln known circuit breakers of this type, the compressed gas circulates in a closed circuit and the system is particularly gastight so as to avoid any leakage of gas towards the outside. The fluid of the circuit breaker is no longer subject to the changes in humidity of the surrounding atmosphere and the operating pressures as well as the nature itself of the fluid can beselected independently of said surrounding atmosphere.

Such arrangements with recovery of the extinction gas and with circulation of the gas entirely isolated from the atmosphere which operate at pressures which are independent of atmospheric pressure are justified only in case of the use of an extinction gas which is poisonous or of high price, such as sulfur hexafluoride which cannot be discharged into the atmosphere. Perfect tightness of the sealing as a matter of fact is costly and difficult to retain for the entire operating life of the .circuit breaker.

An object of the present invention is to provide an electric apparatus which does not require absolute tightness while retaining a circulation system for the extinction fluid which is substantially unafl'ected by the surrounding atmospheric conditions.

The harmful influence of the moisture content of the feed air of pneumatic circuit breakers is well known and particularly the danger of condensation on the insulating walls which gives rise to breakdowns or arc-overs. It follows that the conventional compressor groups for compressed-air circuit breakers must be equipped with water traps and/or devices for drying the air and constitute large bulky installations adapted to treat large quantities of air which after a single use are evacuated into the atmosphere.

It is well known that the drying of air is easily effected by contacting it with absorbent products, but these arrangements are possible only for the treatment of small quantities of air, as the absorption capacity of said products is limited. The frequent replacement or regeneration of the absorbent products would require an amount of work which is incompatible with the normal maintenance of electrical apparatus.

It is an object of the invention to realize a system for recovery of dry air and circulation in a substantially closed circuit which includes a dryer to decrease the stressing of the absorbent material without requiring absolutely gastight circulation circuits.

It is another object of the invention to have the feed air passing continuously through an absorbent filter or drying device inserted in the circulation system, so that once dry it therein deposits only small amounts of moisture resulting from minor leaks which are compensatedfor by the admission of ambient air. Thus, the filter retains its absorbent properties longer the more limited the amount of ambient air entering the circulation system, and the problems of relative tightness are less severe due to the low differences in pressure between the said enclosure and the atmosphere.

Other advantages and characteristics of the invention will become evident from the following description of one embodiment of the invention which is given by way of illustration and not of limitation and is shown in the accompanying drawing.

In the sole FlGURE of the drawing, a compressed-air circuit breaker has two arc-extinguishing chambers 10, 12 born by a hollow supporting insulator 14 which is fastened at its lower part to a low pressure housing or vessel 16 which is located in a zone at ground potential whereby the inside of the insulator l4 communicates hermetically with the reservoir 16. An insulating conduit 18 connects the highand low-voltage zones, extending within the insulator l4, and feeds the chambers 10, 12 with compressed air of high pressure. Depending on the type of circuit breaker employed, the air which is passed through the conduit 18 can feed auxiliary high-pressure reservoirs located in the zone of high potential or directly arc-blast devices or even blast devices and pneumatic control devices for the contacts (not shown) located in the chambers.

Within the low-pressure housing or vessel 16 there is arranged a compressor 20 the intake of which communicates via an absorbent drying filter 22 with the reservoir 16 and the delivery of which, via a conduit 24 in which a drying filter 26 is also contained, feeds a high-pressure reservoir 28 which is also located within the low-pressure reservoir 16. The conduit 18 is connected to the reservoir 28.

A discharge or excess-pressure valve 30 which is urged towards its closed position by a compression spring 32 closes off a discharge orifice 34 of the reservoir 16 in such a manner that it automatically opens upon a predetermined excess pressure within the reservoir 16 and permits the air to escape towards the atmosphere, while preventing any entrance of air into the reservoir 16.

An admission or inlet valve 36 which is urged towards its closed position by a biasing compression spring 38 permits entrance of surrounding air into the reservoir 16 upon a predetermined vacuum in said reservoir, said entrance taking place through a conduit 40 in which an absorbent or drying filter 42 is contained.

The exhaust valves 44, 46 (shown schematically) of the arcextinguishing chambers 10, 12 discharge into a container 48 which communicates hermetically with the inside of the hollow insulator 14. The container 48, the hollow insulator 14 and the housing 16 constitute an enclosure-which will be designated hereinafter by 50-for the recovery of the air escaping from the break chambers l0, 12. The recovery enclosure 50 can communicate with the surrounding atmosphere solely through the admission valve 36 and discharge valve 30. As will be clearer from the following description, the relative tightness of this closure 50 raises scarcely any technical problems, the pressure therein being always close to atmospheric pressure and small leaks being permissible. The normal pressure of the enclosure may be between, for instance, 0.7 and 1.3 bar.

The compressed-air circuit breaker in accordance with the invention operates as follows:

During an operation of the circuit breaker, the high-pressure air admitted into the break chambers l0, l2 and serving inter alia for the blowing of the arcs, escapes through the valves 44, 46 and is collected in the recovery enclosure 50 causing therein an increase in pressure which is insufficient to open the discharge valve 30 (which may open for instance at 2 bars). The high-pressure air supplied to the chambers 10, 12 is taken via the conduit 18 from the high-pressure reservoir 28 and causes therein a drop in pressure which is sufficient to cause the starting up of the compressor 20 which is controlled by a manostate (not shown) sensitive to the high pressure. The compressor 20 draws air through the drying filter 22 from the enclosure 50 and again feeds the high pressure reservoir 28 via the drying filter 26 so as to reestablish therein the rated high pressure which causes the stopping of the compressor and which may be for instance of 15 bars. It is easy to see that the air circulates in a closed circuit, the expanded air which escapes from the break chambers l0, 12 being taken up by the compressor 20 and passed via the conduit 18 into the chambers 10, 12. Upon each cycle the air passes through the drying devices 22, 26 which eliminate any residual moisture from it.

In normal operation, the calibrations of the control manostate of the compressor 20 and of the valves 30, 36 are such that the variations in pressure in the recovery enclosure 50 are maintained within the limits defined by the valves 30, 36 and the latter remain close. The drying products 22, 26 no longer make any contribution as soon as the volume of air included in the closed circuit has bee dried.

In the event of a leakage in the closed circuit towards the surrounding atmosphere, the quantity of gas included in said circuit decreases and the relative vacuum in the enclosure 50 which results from the functioning of the compressor causes the opening of the admission valve 36, set at for instance 0.7 bar and supplying the additional air necessary for the proper operation of the arrangement This new air is dried by passage through the filter 42 and possibly through the filters 22, 26 during the next circulation cycle. The amount of air to be dried is equivalent to the leaks and therefore entirely out of proportion to those used in conventional circuit breakers which discharge all the expanded air to the atmosphere.

A large internal leak of the high-pressure circuit towards the low-pressure circuit may result in an excess of pressure in the enclosure 50 and the opening of the safety valve 30. This discharge of dry air has the same consequences as the aforementioned accidental leaks, namely a decrease inthe quantity of air in the closed circuit which is compensated for upon the placing in operation of the compressor 20 by admission of air through the valve 36. A small internal leak will have no effect on the air-drying devices, the dry air escaping from the high pressure being automatically recovered in the enclosure 50 and therefore maintained within the normal circulation circuit. The only effect is a more frequent operation of the compressor.

The entrance of surrounding air into the enclosure 50 through a path other than the admission valve 36, for instance through a defective joint, may cause an increase in the moisture content which is rapidly eliminated by the filters 22 and 26.

it will now be understood that the tightness of the enclosure 50 need not be entirely perfect, as the drying filters make up for the small defects and the pressures or vacuums acting on the walls of the enclosure 50 are limited.

The present invention has been described in connection with the preferred embodiment illustrated in the FIGURE, but

it is to be understood that numerous variants may be made therein without going beyond the scope of the invention.

In accordance with the embodiment described, the air treatment device comprises moisture-absorbing products, but any other conventional device for the removal of water can be used and the treatment of the air may extend to the elimination of any product or component which is harmful to the satisfactory operation of the circuit breaker, for instance dust or corrosive products.

In the foregoing disclosure, a circuit interrupter has been discussed in connection with the invention. it should be understood that the invention can also be embodied in another electric apparatus such as a short-circuiting device working in a high pressure air environment but without gas blast.

What is claimed is:

l. A compressed air electric apparatus disposed in atmospheric air and comprising a high-pressure compressed air enclosure and a contiguous low-pressure air vessel, compressor means compressing air taken from said low-pressure vessel to supply compressed gas to said high-pressure enclosure, norrrially closed valve means for controlling the admission of atmospheric air to said low-pressure vessel, biasing means to bias said valve means towards its closed position, pressure sensitive means to cause the opening of said valve means against the action of said biasing means as the pressure in said lowpressure vessel drops below a predetermined pressure, said predetermined pressure being less than the pressure of said atmospheric air, and an air-drying device to have said compressor means supplying substantially dried compressed air to said high pressure enclosure.

2. An electric apparatus according to claim 1, further comprising discharge valve means to discharge air from said lowpressure vessel as the pressure in said vessel rises above a predetermined pressure value.

3. An electric apparatus according to claim I, further comprising an air-drying device connected to said valve means to dry the air flowing through said valve means.

4. A compressed-air circuit interrupter comprising airblast arc-extinguishing means supplied with high-pressure air delivered b compressor means, a low pressure air container to collect t e air exhausted from said arc-extinguishing extinguishing means, said compressor means taking air from said low-pressure container, normally closed valve means for controlling the admission of atmospheric air to said low-pressure vessel, biasing means to bias said valve means towards its closed position, pressure-sensitive means to cause the opening of said valve means against the action of said biasing means as the pressure in said low-pressure vessel drops below a predetermined pressure, said predetennined pressure being less than the pressure of said atmospheric air, and an air drying device to have said compressor means supplying substantially dried compressed air to said high-pressure enclosure. 

1. A compressed air electric apparatus disposed in atmospheric air and comprising a high-pressure compressed air enclosure and a contiguous low-pressure air vessel, compressor means compressing air taken from said low-pressure vessel to supply compressed gas to said high-pressure enclosure, normally closed valve means for controlling the admission of atmospheric air to said low-pressure vessel, biasing means to bias said valve means towards its closed position, pressure sensitive means to cause the opening of said valve means against the action of said biasing means as the pressure in said low-pressure vessel drops below a predetermined pressure, said predetermined pressure being less than the pressure of said atmospheric air, and an air-drying device to have said compressor means supplying substantially dried compressed air to said high pressure enclosure.
 2. An electric apparatus according to claim 1, further comprising discharge valve means to discharge air from said low-pressure vessel as the pressure in said vessel rises above a predetermined pressure value.
 3. An electric apparatus according to claim 1, further comprising an air-drying device connected to said valve means to dry the air flowing through said valve means.
 4. A compressed-air circuit interrupter comprising airblast arc-extinguishing means supplied with high-pressure air delivered by compressor means, a low pressure air container to collect the air exhausted from said arc-extinguishing means, said compressor means taking air from said low-pressure container, normally closed valve means for controlling the admission of atmospheric air to said low-pressure vessel, biasing means to bias said valve means towards its closed position, pressure-sensitive means to cause the opening of said valve means against the action of said biasing means as the pressure in said low-pressure vessel drops below a predetermined pressure, said predetermined pressure being less than the pressure of said atmospheric air, and an air drying device to have said compressor means supplying substantially dried compressed air to said high-pressure enclosure. 